The goal of this proposal is to develop a rapid, reliable and high- throughput Fragile-X carrier screening assay suitable for clinical settings. The prevalence of Fragile-X syndrome underscores the importance of a reliable carrier screening assay. A homogeneous system based on DNA amplification (PcR) and concomitant detection, AmpliSensor Assay, has been developed in Biotronics. We have demonstrated that the extent of CGG expansion can be detected by a comparative AmpliSensor Assay analysis of Fragile-X specific gene against a reference gene. Phase I study aims to (a) establish the validity of a cut-off standard to define the carrier status; (b) determine the resolution of the assay for detecting mosaic samples; (c) formulate the sample preparation protocol for assay using Guthrie card dry blood sample; and (d) establish a relative allele copy number of amplifiable FMR-1 gene against X-chromosome specific gene as reference gene for carrier phenotypes. In phase ll, research will focus on the methodology and format to be applied in a clinical setting and to complete the development of a diagnostic software program for the comparative quantitative AmpliSensor assay. The ultimate goal of this project is to develop a complete diagnostic kit which can be used for a routine clinical Fragile-X carrier screening. PROPOSED COMMERCIAL APPLICATIONS A reliable, clinically accepted DNA-based amplification assay for the screening of Fragile-X carrier has not yet been available. The proposed comparative quantitative PCR Fragile-X carrier detection format can provide clinics with a rapid, reliable and inexpensive screening test to replace the direct PCR detection and Southern blotting analysis as the standard Fragile-X carrier test.